Combing 18F FDG PET•CT and CT Perfusion in a Case of Lung Cancer

Case example to assess the relationship of glucose uptake to the degree of tumor proliferation

Alexander W. Sauter, MD

Case study data provided by Eberhard Karls University, Tübingen, Germany

 |  Dec 18, 2012

Introduction
Lung cancer is the leading cause of cancer death worldwide. Tumor angiogenesis plays an important role in tumor behavior, especially with tumor growth and metastatic potential in lung cancer. Newer drugs primarily targeting tumor angiogenesis aim to provide individualized treatment for non-small cell lung carcinoma (NSCLC). Incorporation of anti-angiogenic drugs in the therapy regime requires information not only of tumor extent and metabolism, but also of tumor vascularity and perfusion. This demands multiparametric tumor profiling in order to predict tumor aggressiveness, response potential and prognosis. The clinical example discussed below demonstrates the combination of fludeoxyglucose F 18 (18F FDG) injection* PET•CT and CT perfusion in a case of lung cancer that delivers complementary information potentially relevant to anti-angiogenic therapy.

 

*Siemens' PETNET Solutions is a manufacturer of fludeoxyglucose F 18 injection (18F FDG). Indication and important safety information as approved by the US Food and Drug Administration can be found at the bottom of the page for 18F FDG, adult dose 5-10 mCi, administered by intravenous injection.

 

History
A 77-year-old man with adenocarcinoma in the left lung underwent PET•CT performed on a Biograph™ TruePoint 16 PET•CT system 55 min following 342 MBq 18F FDG injection. The acquisition started with a biphasic contrast enhanced CT with an arterial phase acquisition of the thorax, followed by a venous phase acquisition of the abdomen and pelvis. A low-dose CT scan was used for attenuation correction. Whole-body PET acquisition was performed for 3 minutes per bed position.

Examination Protocol

Scanner: Biograph TruePoint 16
Dose: 9 mCi 18F FDG
Scan Delay: 64 frames, 15 sec/frame
Parameters: 3 min per bed position
CT Perfusion: Contrast flow 5 ml/sec 0.3 sec temporal resolution

SOMATOM Definition AS+ 

 

Diagnosis
An arterial phase contrast CT image (Figure 1) of the lung shows a large chest mass in the left lower lobe with connection to the hilum and a low contrast enhancement in the central part compared to the tumor periphery. The lung window setting discloses surrounding opacities related to pneumonia or tumor extension. The fused PET•CT image shows high glucose metabolism toward the medial and peripheral aspect of the tumor, with decreased uptake in the center and laterally, possibly related to tumor necrosis. The arterial phase CT and 18F FDG PET correlate well regarding the definition of the necrotic zone. SUVmax was 5.2, metabolic tumor volume (at 50% isocontour) was 2.6 ml, while the total tumor volume calculated from the CT was 3.6 ml. All values were calculated using syngo® TrueD. The patient subsequently underwent a CT perfusion study using a 128-slice CT system (SOMATOM® Definition AS+) using adaptive spiral technique. Contrast was injected at a flow rate of 5 ml/sec. Total acquisition time was 40 sec. Data evaluation was performed using syngo Volume Perfusion CT Body. After automatic application of motion correction and noise reduction of the datasets, color-coded maps were generated for tumor blood flow (BF), blood volume (BV) and flow extraction product (Ktrans).

Fig. 2: CT perfusion parametric images show increased blood flow and blood volume in the medial and outermost tumor parts, with decreased values in the center and toward the lateral margin. There seems to be a correlation with the 18F FDG distribution. However, there are tumor parts more centrally located that have a high 18F FDG uptake and low perfusion. Additionally, areas with low perfusion do not exclusively correspond to necrosis, but potentially also to hypoxia.

 

Comments
This clinical example is one of a series of 24 consecutive patients of NSCLC studied with 18F FDG PET•CT and CT perfusion by Sauter et al.1 SUVmax, SUVmean and metabolic tumor volume were used as quantitative markers for 18F FDG uptake. CT perfusion parameters like mean and max BF, BV and Ktrans, along with 18F FDG uptake values, were compared with histologic subtypes, proliferation marker Ki67 and microvessel density (MVD). Both Ki67 and MVD are accepted as a histological marker for tumor aggressiveness. In the adenocarcinoma group, SUVmean and SUVmax were 5.8 and 8.7, and in squamous cell carcinoma (SCC) 8.5 and 12.9, respectively. Mean BF (mL/100 mL/ min), mean BV (mL/100mL), and Ktrans (mL/100 mL/min) were 35.4, 7.3 and 27.8, in adenocarcinoma and 35.5, 10.0 and 27.8, respectively, in SCC. There was no significant difference between the parameters of the two subgroups, except SUVmean with a 3D freeform Volume of Interest (VOI). SUVmean and SUVmax demonstrated positive correlation with Ki67, thereby reflecting the relationship of glucose uptake level to the degree of tumor proliferation in lung cancer, although additional factors like inflammatory and hypoxic components influence glucose uptake as well. CT perfusion parameters like BF and BV correlated with MVD, thereby reflecting the potential of CT perfusion to detect tumor angiogenesis. On the other hand, 18F FDG uptake and MVD, as well as perfusion parameters and Ki67, revealed no correlation. Therefore, both modalities provide complementary information. This study was performed with PET•CT, with CT perfusion performed on different systems. However, Biograph combines the capability of performing CT perfusion with high temporal resolution, along with high-efficiency and high-resolution PET, for an optimized approach to imaging for multiparametric tumor profiling, as depicted in this case study.

 

Reference

  1. Sauter et al. JNM 2012 Apr; 53(4):521-9

 

* Fludeoxyglucose F 18 Injection

 

INDICATIONS AND USAGE

Fludeoxyglucose F 18 injection (18F FDG) is indicated for positron emission tomography (PET) imaging in the following setting:

Oncology: For assessment of abnormal glucose metabolism to assist in the evaluation of malignancy in patients with known or suspected abnormalities found by other testing modalities, or in patients with an existing diagnosis of cancer.

 

IMPORTANT SAFETY INFORMATION

Radiation Risks
Radiation-emitting products, including fludeoxyglucose F 18 injection, may increase the risk for cancer, especially in pediatric patients. Use the smallest dose necessary for imaging and ensure safe handling to protect the patient and health care worker.

Blood Glucose Abnormalities
In the oncology and neurology setting, suboptimal imaging may occur in patients with inadequately regulated blood glucose levels. In these patients, consider medical therapy and laboratory testing to assure at least two days of normoglycemia prior to fludeoxyglucose F18 injection administration.

Adverse Reactions
Hypersensitivity reactions with pruritus, edema and rash have been reported; have emergency resuscitation equipment and personnel immediately available.

 

Full Prescribing Information Fludeoxyglucose F 18 Injection
 

Fludeoxyglucose F 18 injection is manufactured by Siemens' PETNET Solutions, 810 Innovation Drive, Knoxville, TN 39732

The statements by Siemens customers described herein are based on results that were achieved in the customer's unique setting. Since there is no "typical" hospital and many variables exist (e.g., hospital size, case mix, level of IT adoption) there can be no guarantee that other customers will achieve the same results.